使用反射魔术

Question

我有List<>个对象，其类型为我的类Car。类Car具有12个属性。我有7个TextBox，用户可以在此处输入搜索值（某些属性）。如何通过该列表进行搜索以获得与输入的所有数据匹配的对象？
我已经尝试过这样的事情：

foreach (Car x in Cars)
{
   //then here I question every attribute with search value which match I add to new List<>
   if(x.color == textBox1.Text) search.Add(x); 
}

textBox1是用户输入的值之一。当用户仅输入一个值时，此方法有效。如果输入两个值，它将找到具有两个值中任何一个的所有对象。但是我想找到两个值都匹配的对象。

Answer 1

如果要检查是否输入了过滤器值，请执行此操作

IEnumerable<Car> filteredCars = Cars;

if(!String.IsNullOrWhiteSpace(textBox1.Text))
   filteredCars = filteredCars.Where(car=>car.param == textBox1.Text);

if(!String.IsNullOrWhiteSpace(textBox2.Text))
   filteredCars = filteredCars.Where(car=>car.param2 == textBox2.Text);

最后

var result = filteredCars.ToList()

仅执行一次ToList（最后一次）

Answer 2

使用反射魔术

我想你想要这样的结果吗？

我没有自动生成TextBox，但是那很容易。

MainWindow.xaml

<StackPanel x:Name="MainGrid" Width="200" Margin="100">
    <TextBlock Text="Color" />
    <TextBox x:Name="ColorTextBox"></TextBox>
    <TextBlock Text="Make" />
    <TextBox x:Name="MakeTextBox"></TextBox>
    <TextBlock Text="Interior" />
    <TextBox x:Name="InteriorTextBox"></TextBox>
    <Button x:Name="SearchButton" Content="Search" Click="SearchButton_Click"></Button>
    <TextBlock x:Name="SearchResultTextBlock"></TextBlock>
</StackPanel>

MainWindow.xaml.cs

private void SearchButton_Click(object sender, RoutedEventArgs e)
{
    Car[] allCars = new Car[] // Sample list of cars
    {
        new Car
        {
            Color = "Green",
            Make = "Ford",
            Interior = "Stone"
        },
        new Car
        {
            Color = "Green",
            Make = "Ford",
            Interior = "Wood"
        },
        new Car
        {
            Color = "Black",
            Make = "Cadillac",
            Interior = "Stone"
        },
        new Car
        {
            Color = "Black",
            Make = "Volvo",
            Interior = "Stone"
        },
        new Car
        {
            Color = "Green",
            Make = "Volvo",
            Interior = "Wood"
        },
        new Car
        {
            Color = "Green",
            Make = "Volvo",
            Interior = "Plastic"
        },
    };

    var result = _filterWithInputs(allCars); // Search the list

    SearchResultTextBlock.Text = $"Found {result.Length} matching cars."; // Output
}

private Car[] _filterWithInputs(IEnumerable<Car> allCars)
{
    List<Car> result = new List<Car>();

    // Get the TextBoxes from the viow
    List<TextBox> textBoxes = new List<TextBox>();
    foreach (var mainGridChild in MainGrid.Children)
    {
        if(mainGridChild is TextBox)
            textBoxes.Add(mainGridChild as TextBox);
    }

    // Search the allCars collection.
    foreach (var car in allCars)
    {
        if (_checkCarAgainstNamedTextBoxes(car, textBoxes))
            result.Add(car);
    }

    Debug.WriteLine($"Found {result.Count} matching cars.");

    // Return the result as a fixed-size array.
    return result.ToArray();
}

private static bool _checkCarAgainstNamedTextBoxes(Car car, IEnumerable<TextBox> textBoxes)
{
    foreach (TextBox textBox in textBoxes)
    {
        // Skip empty TextBokes (succees)
        if(string.IsNullOrWhiteSpace(textBox.Text))
            continue;

        var propertyName = textBox.Name.Replace("TextBox", "");

        // Assume all Car properties are strings
        var val = car.GetType().GetProperty(propertyName)?.GetValue(car) as string;

        // If the text doesn't match (case-sesitive) return false
        // No need to check any more properties after first fail.
        if (val != textBox.Text)
            return false;
    }

    return true; // Everything succeeded!
}

神奇之处在于_checkCarAgainstNamedTextBoxes，其中将TextBokes的前缀与Car类的属性名称进行比较。

如果将TextBox命名为ColorTextBox，则将其值与汽车的Color属性进行比较。

文本框必须直接位于MainGrid下才能显示在“儿童”集合中。递归很容易搜索多个级别。

Answer 3

我将创建一个可以处理null的参数值列表，并在单个查询中执行：

string color = String.IsNullOrEmpty(textColor.Text) ? null : textColor.Text;
string engine = String.IsNullOrEmpty(textEngine.Text) ? null : textEngine.Text;

var filteredList = cars.Where(c => (color == null || c.Color == color) &&
                                   (engine == null || c.Engine == engine)).ToList();

对其他文本框执行相同的操作。

Answer 4

使用LINQ时，可以根据所选条件逐步扩展查询：

$end

之所以可行，是因为您可以修改LINQ查询，直到实现它为止。在这种情况下，您在执行之前先在之前添加所有选定的过滤条件。最后一步，您用var carsQry = from car in Cars select car; //Filter by color if (!String.IsNullOrWhiteSpace(textBox1.Text)) { carsQry = from car in carsQry where cars.color == textBox1.Text.Trim() select car; } //...repeat step above for all other filter criteria... List<Car> filteredCars = carsQry.ToList();实现（=执行）它。返回的列表将包含您过滤的项目。

如何使用多个参数对对象列表执行搜索？

4 个答案:

使用反射魔术